An off-highway vehicle, such as a locomotive, a mining truck, or a marine vehicle, may include an engine having a turbocharger that is designed to have greater efficiency at the most frequent engine operating conditions. However, such designs may result in lower efficiency at a less common engine operating condition. For example, a vehicle may have a turbocharger with greater efficiency at peak output power than at lower power output. Specifically, the turbocharger compressor and/or turbine may be shaped to optimize flow at higher speeds and pressure ratios, thereby resulting in improved engine efficiency where the engine operates most.
The inventors herein have recognized that even though such turbocharger designs may optimize performance overall, engine performance may be degraded at some operating regions, such as mid speed and mid load regions.